1. Field of the Invention
The invention relates to a process for treating tobacco stems and more particularly relates to a process which involves the steps of shredding the tobacco in a disc shredder while controlling the specific energy imparted to the tobacco by the disc shredder and drying the shredded tobacco under high humidity conditions.
2. Brief Description of the Prior Art
In the manufacture of smoking articles which include some preselected percentage of tobacco stems, it is the usual practice to moisten such stems to minimize shattering and provide a material of more uniform particle size prior to reducing the stems to a particle size of a preselected dimension appropriate for preparing the smoking articles in which the stems are to be included. After the stems have been moistened and reduced to the preselected particle size, it also is necessary to reduce the moisture content of the tobacco stems to a level below that in which the size reduction is conducted.
One of the manners of reducing stems to a preselected particle size is by shredding the stems prior to further treatment in order to fiberize the stem and provide increased filling capacity. Various methods are known in the art to accomplish this shredding reduction. For example, the now expired U.S. Pat. No. 3,204,641 issued to S. O'Brien Jones on Sept. 7, 1965, teaches a method of producing tobacco leaf stems by adjusting the moisture content of the stems in the percentage range of about 40% to about 65% by weight and then shredding the moistened stems to a preselected size suitable for cigarettes before drying the material to a moisture content suitable for use in cigarettes. U.S. Pat. No. 4,094,323 issued to Frazier et al, on June 13, 1978, teaches a method of moistening tobacco stems in a percentage range from about 10% to about 50% by weight while maintaining the temperatures of the stems in a range of from about 115.degree. to about 170.degree. C. at a preselected pressure of 10 to 100 psig and then mechanically fiberizing the treated stems under such pressure by shredding. U.S. Pat. No. 4,195,646 issued to G. F. Kite on Apr. 1, 1980, teaches a method of shredding tobacco stems by splitting the stems lengthwise along the grain by supporting the stem shards in a fluid medium and striking the shards with a blunt instrument to separate such shards into fibrilliform shred fragments. In addition, U.S. Pat. No. 4,386,617 and UK Patent Application No. 2,078,085, published for inspection on 6 Jan. 1982, both to Warren Arthur Brackman, teach a method of soaking tobacco stems to provide a moisture content by weight of 30% to 60%, shredding the soaked stems and then drying the stems to a moisture content desired, the stems having been brought to a temperature up to the boiling point of water prior to such shredding step.
As can be seen from this aforediscussed prior art, it has long been known in the tobacco processing art, to shred tobacco stems which have been moistened to a preselected range and then to reduce the moisture content of the shreds to a desired level for the smoking article in which the shredded stems are to be included. The reduction of the stems to the desired moisture content has been accomplished by conventional drying means in the conventional manner to obtain the desired result.
A number of processes also are known in the art for heating and drying moistened tobacco particulates arrived at by cutting and rolling and by subjecting the particulates to heated gas streams held at preselected temperatures. For example, U.S. Pat. No. 3,357,436, issued on Dec. 12, 1967, to A. H. Wright and German-Ausleggeschrift 2,253,882, teach processes wherein moistened, cut tobacco ribs have been moistened in the range of from about 24% to 40% by weight and then dried by gases at a temperature of from 121.degree. C. to 370.degree. C. for brief periods of time ranging from 0.3 to 3 seconds to reach moisture contents by weight as low as 6% within a short period of time. U.S. Pat. No. 3,734,104, issued to Buchanan et al, on May 22, 1973, teaches the treating of rolled, crushed tobacco stems, which have been moistened to a content of about 24% to 60% by weight, with a hot gas stream containing at least 30% steam to heat the stems to about 0.5 to less than 3 seconds. Further, more recent U.S. Pat. No. 4,167,191, issued to John Jewell, et al, on Sept. 11, 1979, teaches a process of drying expanded cut tobacco at a temperature within the range of from about 250.degree. F. to about 650.degree. F. in the presence of an absolute humidity at a level above that which will provide a wet-bulb temperature of at least about 150.degree. F.
As can be seen from the aforediscussed, these varying drying processes of the more recent past have been utilized in conjunction with cut tobacco leaf lamina and stems, all of which have been cut to a preselected size.
The present invention recognizes that it has been a desideratum of past tobacco stem shredding processes to optimize the economic use of the stems in smoking articles by converting the stems into a product suitable for inclusion as a smoking article filler with as high a fill value (FV) as possible. In addition, the present invention recognizes that it has been a desideratum of past high humidity drying as aforedescribed to reduce the moisture content of expanded tobacco generally to a desired level, while minimizing possible loss in filling power. By recognizing the aims of these two separate processing systems the present invention uniquely combines the several steps of each into a novel combination of steps to obtain fill values heretofore unknown in the art.
The present invention further provides a novel, economic and straightforward series of steps for treating tobacco stems to reduce their particulate size and yet at the same time to optimize their fill value for smoking article purposes.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth hereinafter.